What is the best way to determine if an endotracheal has been properly positioned in the patient? For generations the gold standard has been the presence of bilateral breath sounds with auscultation of the chest wall. At least that was the answer when asked during oral boards examination. But as most anesthesiologists know, that is an imprecise determination. The operating room can be a very noisy environment. One may have trouble hearing any breath sounds at all. The chest wall can also easily transmit breath sounds from one side of the chest to the other in a thin patient.
A research abstract out of the Medical University of Vienna General Hospital (Anesthesiology News, May 2011) found that anesthesiology residents were able to accurately place an ETT by auscultation alone only half the time. By contrast, the correct placement of an ETT by looking at tube depth was 88%. The sensitivity for auscultation was 65% and for observation of bilateral chest wall movement was only 43%. However, if all three procedures were done, the ETT was placed correctly in nearly 100% of patients.
Previously, residents were taught that the best tube depth was 21 cm at the lips for women, 23 cm for men. The researchers found that this led to the tip of the tube being uncomfortably close to the carina, less than 2.5 cm (1 inch) from the bifurcation. Their new recommendation is 20/22 cm. But from personal experience, learned painfully, even this is not always accurate.
I remember taking care of a trauma patient one night. The patient was a short adult female with multiple stab wounds in the torso, including the left shoulder. Shortly after intubation, the patient started desaturating. Instinctively, I listened for breath sounds. They were much diminished on the left side. Therefore I pulled the tube back. The O2 sat improved slightly, but it never came back up to 100%. Auscultation again revealed decreased breath sounds on the left side. Again I pulled the tube back. Now the tube depth was only 18 cm at the lips and the O2 sat was not coming up. In fact it was steadily dropping and now the blood pressure was falling too.
With the patient's left sided chest injuries, the next logical conclusion was that there was a tension pneumothorax on the left side. A needle was inserted into the left chest. But there was no hiss of escaping air. The oxygen sat kept falling. The surgeons then quickly placed a thoracostomy tube into the chest but no blood or air returned. They then made a full thoracotomy incision and reached into the thoracic cavity. They found that the left lung was collapsed and not inflating at all. A fiberoptic bronchoscope was quickly retrieved and placed down the ETT. The tube was clearly still down the right main stem bronchus. It was then pulled back until the carina was visible through the scope. The left lung started inflating normally and the patient's O2 sat regained 100%. The tube was then taped securely, at 15 cm at the lips.
This goes to show that even when every standard precaution was made, an ETT can still be placed incorrectly. The new gold standard for proper placement should be a fiberoptic bronchoscope. We do this for every double lumen tube placement. The same principle should apply for every questionable intubation.